Condition controller



Nov. 4, 1941. J. E.HA|NES 2,261,582

CONDITION' CONTROLLER Filed Nov. 2, 193e;

BLACK SURFACE 105 Invento Aitornezy Patented Nov. 4, 1941 parrafos'mrlss PATENT OFFICE coNnrrroN comentan John n. naines, Minnmsous,man., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis,man., a corporation of Delaware A application Novemoer z, 193s, seraiN0. masso 3 claims. (ci. zeef-ssi The present invention relates tocondition controlling devices, and more particularly todevices forcontrolling the temperature or humidity of spaces occupied-by humanbeings in order to maintain comfortable conditions therein.

Heretofore, it has been customary to merely maintain a constant dry bulbtemperature in somewhat satisfactory, at times causes the occupants toexperience a somewhat chilly sensation, while at other times to feel toowarm. The reasons for this is that dry bulb temperature is not the solefactor affecting the comfort of the occupants.

As is well known, heat is constantly generated within the human body,and must constantly be dissipated therefrom. This heat is dissipated byradiation, by conduction, and by the evaporation of moisture on theskin. If the conditions within the space are such that the dissipationof heat from the human body would be rapid, the temperatur controllingglands of the body itself would act to compensate for suchcondition,'but

crease in heat dissipation, which causes the. oc-

cupants to feel too warm.

ift

nevertheless, the person would feel chilly. Conversely, if theconditions within the space are such that heat dissipation from the bodywould be slow, perspiration would increase and the person would feelwarm and. uncomfortable. If, however, the conditions within the room aresuch that the proper dissipation of heat from the body is obtainedwithout the necessity of the temperature controlling organs of the bodyvfunctioning to a. great extent one way or the other, the person willfeel very comfortable. In other words, a

comfortable space condition is one in which the normal dissipation ofheat from the human body is obtained without substantial effort on thepart of the body temperature controlling system.

While the rate of dissipation of heat from the human body is aec'tedprimarily by the temperature of the surroundingV air, it is alsoappreciably adected by other conditions such asrelative humidity, aircurrents, and the temperature of the walls or other physical objectswithin the enclosure. Ii the relative humidity is low, evaporation ofmoisture from the skin will be increased, thus causing the occupants tofeel chilly even though the temperature of the surrounding ai! iS'abOve70 F. Similarly, if the relative hlimidity is high; evaporation ofmoisture from' the will be decreased. thus resoltingin a `de- 55the'space may be brought' into orvtaken out et 'Air currents alsoaect'the rate of heat dissipation from the body. Due to a draftycondition, the increased air flow across the body causes an increase inthe rate of evaporation of moisture from the skin, and further increasesthe heat loss due to conduction or connection. Thus a drafty conditionwould cause the occupants to feel chilly, even though the temperature ofthe air is not low. Conversely, with extremely still air, the heatlossis reduced, and may cause the occupants to feelwarm eventhough theair temperature is not excessive.

The temperature of the walls and objects within the room `also aects therate oi heat dissipation from the human body andconsequently aff fectshuman comfort. As heat will be transferred by radiation from a bodyofhigher temperature to a body of lowertemperature, heat is alwaysradiated from the `human body to the walls and to physical objectswithin the room if' such objects are lower in temperature than bodytemperature. The rate of heattransfer of course is dependent upon thediierence in temperature. Hence in cold weather when the walls arerelatively cold, the heat dissipation from the human body is increased,thereby causing the occupants to feel chilly, even though thetemperature may be above F. Conversely, if the walls are heated eitherartificially as by panel heating in winter, or by warm weather, theradiation of heat from the occupants would decrease, or heat may even beradiated to the occupants thus caus z ing them to feel too warm eventhough the room the walls and objects vWithin the enclosure, while atthe same time, heat is being radiated to the body from a warmer objectsuch, for instance, 'as a. stov/e or radiator. 'I'he effect of radiationon the comfort of the occupants would thus be the resultant of these twoactions. Y

From the foregoing ,it is yapparent that in order to maintains. space ata condition of maximum comfort, it is necessary to take intoconsideration the temperature, humidity, and air currents in the spaceoccupied, and also what may be termed as the resultant radiation to orfrom the occupants. It should alsobe apparent that comfort conditionsmay be maintained in a space without maintaining any of` the abovementioned factors constant, and that by changing the value of any onefactor, the condition of the comfort zone. What may be termed the ihdexof comfort is thus the resultant on human comfort of the four factorsenumerated.

The primary object of my invention, therefore, is to provide a controldevice whichris affected by temperature, humidity, and air` currentswithin the room, and which is further affected by the temperature of thewalls and objects within the enclosure.

More specifically, it is an object of my invention to provide a controldevice which imitates,l

as nearly as possible, the heat loss from` the human body, and which isadapted to control one or more of the various factors above mentioned inorder to maintain the space in a comfortable condition.

A furtherv object is to provide a condition controlling or measuringdevice which directly measures the index of comfort of a space.

Another object is to provide a condition lcontroller which is affectednot only by the temperature surrounding the controller, but also by thetemperature of other objects in the space in which the controller islocated.

Other objects will appear as this description proceeds.

For a complete description of my invention reference is made to theaccompanying drawing, in which:

Figure l is an elevation partly in section .of a

,preferred form of a condition responsive device;

Figure 2 is a wiring diagram indicating the connections of the device ofFigure 1 with a condition controlling system: and

Figure 3 is a sectional elevation of a different form of thermostatembodying one of the fea- .tures of my invention.

Reference character I indicates a circular base member. This base memberis provided with an upstanding boss 2 having therein anaperture 3 whichextends through to the opposite side of the base member. Member I isshaped with a stepped lower surface providing an outer shoulder 5 and anannular surface 4 at right angles thereto, a second shoulder 1, and acooperating annular surface 6 at right angles thereto. The surface 5 isscrew threaded to cooperate with the threads of a ring 9 which issecured to a dome shaped outer jacket 3 which is formed of a porousmaterial such as Alundum. Between the surface 5' and the upper edge-ofporous jacket 8 is inserted a gasket Il which may be of soft rubber orother suitable material. 'I'he surface 1 is screw threaded to receive adome shaped inner jacket II which is formed of a heat conductingmaterial. A gasket I2 is interposed between the end of this Vmember andthe shoulder 8, thereby forming a water tight connection. As shown thejacket 8 is spaced from the member II thereby'providing a space I3 whichis adapted to receive water through a passage Il leading through thebase member I to the a`perture'3. the'end of said passage being securedto a water supplying tube I5.

'I'he inner surface of the member I I is recessed at Il to receive anannular shaped heating element I3. desired form, and is herein shown ascomprising a resistance coil wound around a core 2l. This heatingelement should be secured to the membei` II by means of a heatconducting cement so that the heat from the coil flows directly into themember II' thereby causing member II to be- 'come heated. The member IIis shown as hav- Heating element I8 may be of any.

solely to the temperature of the mass II.

duction of heat therethrough, thereby causing it to be substantiallyequally heated throughout even though the heating element is localized.It will be observed that the heating element is located substantiallyequi-distant between the ends of member II and contacts the entire innercircumference of said member, thereby causing substantial equalizeddistribution of heat to the extremities of said member. s

Mounted upon base member I adjacent aperture 3 is an L shaped supportingelement 26, this member being secured to the base member I by means of ascrew 25. Attached to the other leg of member 25 isa bimetaliic element21 which extends downwardly. To the lower end of the bimetallic element21 is attached a flexible contact blhde 23 carrying a contact 23.Between the ends of the bimetallic element 21 is attached a relativelystiff contact blade 3l which carries a contact 3I. Attached to the basemember I and facing the bimetallic element 21 is an L shaped contactcarrying arm 33 which is formed of insulating material and which issecured to the base member I by means of a screw 34. Member 33 at itsother extremity carries an adjustable contact point 3l cooperating withthe contact 28, and a second adjustable contact 35 which cooperates withthe contact 3l.. The bimetallic element 21, it will be seen, iscompletely surrounded by the element II which forms a mass of heatconducting material. Bimetallic element 21 is responsive to only thetemperature of the mass of element Il; Should the mass temperature behigher than the temperature of thel bimetallic element 21, heat will beradiated from the former' to the latter until the mass and thethermostatic element are of the same temperature. Conversely, should thetemperature of the thermostatic element 21 be higher than that of massII radiation of heat from the former to the latter will occur until thethermostaticv element and mass are again of equal temperature. By thisaction the thermostatic element 21 responds heating element will notmaterially affect the thermostatic element 21 due to the fact that thiselement is in good heat conducting relationship with the mass ofmaterial II. It is to be understood that this element will not beintensely heated but is to be heated just suilleiently to cause thedesired input of heat into the mass II. If desired, the interior surfaceof the heating element maybe covered with an insulating material inorder to prevent any possibility of its affecting the thermostaticelement 21. Thermostatic element 21 may be arranged to move towards theright upon aI decrease in temperature and the contact points 35 and 39may be adjusted so that contacts 38 and 29 are engaged rst and upon afurther fall in temperature the contact points 3i and 35 will engage.

The device as a whole is intended to be locatedy in a position withinthe room wherein it will be subjected to the air currents. within theroom and wherein it may receive or admit heat by radiation from or tosurrounding objects in the room. For this purpose I prefer to locate thedevice in about the center of the room, and may` hang it from theceiling by means of a pipe or conduit 4i which is inserted into theaperture 3 of the base member I. Conduit Il is to be fixed in anysuitable manner to the ceiling of the space in which the control deviceis located. The various leads 4I for 6e' heating element. thermoingsumcient mass to cause substantialcon- 1I .um element, and mene pome.may be led The wire I to line wire 52.

through the conduit 45 along with the water supplying tube I5. Ifdesired, a plug 42 of insulating material'may be placed within aperture3 to prevent escape of heat from the interior oi the mass element I Iinto the conduit 45.

In order to maintain a'constant head of water ln the space I3 I providea constant water level device 43 which is' connected to the watersupplying pipe I5. The constant water level maintaining device maycomprise an open ended'tube 44 having therein an overflow pipe 45leading to any suitable drain. Water is supplied to the tube 44 by meansof a supply pipe 45 having therein a needle' valve`41. By adjustingvalve 41 to maintain a slight overflow of water over the end of overflowpipe 45 the level of water in chamber 44 may constantly be maintained ata` level equal to the height of overflow tube 45. In this manner aconstant supply of water at a c onstant pressure is maintained for thecontrol device. v

In Figure 2 I have shown the wiring connections between the thermostatand a condition controlling device which, in this 4case may be a gasvalve 50. Gas valve 55 is of the type which opens when energized andwhich closes upon deenergization thereof. 'I'his valve is controlled bymeans of a relay generally indicated at 5I. Relay 5I comprises a coil 52and an armature 53 disposed in the Velectrical field of the coil 52. u

Armature 53 is pivotally connected by a link 54 to a pair of switch arms55 and 55. Switch arm 55 is pivoted at 51 and at its'other endcooperateswith a holding contact 55. Switch arm 55 is similarly pivoted at 55 andcooperates with a contact 55. When relay coil 52 is energized thearmature 53 is pulled to the right, thereby moving contact arms 55 and55 into engagement with the contacts 55 and 55. Upon deenergization ofrelay coil 52 the switch arms 55 and 55 will be moved from engagementwith contact'points 55 and 55 by means of a spring, not shown. o

One terminal of the valve 55 Ais connected by a The other terminal ofsaid valve is connected by a' wire 55 with switch arm 55 while thecontact 55 cooperating with switch'arm 55 is connected by a wire 54 withthe line wire 55. Thus, when contact arm 55 is moved into engagementwith contact 55 thevalve 55 is energized and thereby caused to open forsupplying gas to the burner, not shown.

The `:ight-hand end of relay coil 52 is connected by wires 55 and 51 tothe contact point 35 of the thermostat. while the other end of relaycoil 52 is connected by a wire 55 with oneend ofthe low voltagesecondary 55 of a step-down transformer 15. The other end of thetransformer secondary l55 is connected by a wire 1I with the contactpoint 34. The bimetallic element 21 is connected by a wire 12 to theholding contact 55 of relay 5I while the switch arm 55 which cooperateswith holding contact 55 is connected by a wire 13 to the junction ofwires 55 and 51.

In operation, as the temperature surrounding thermostatic element 21falls, this element will relay coil 52, and wire 55 to the left-hand endoi' transformer secondary 55. Upon energization of relay coil 52theamature 53 will move warp towards the right ther/eby bringing contactgizing circuit for the relay coil 52 will then be closed, this circuitbeing traced as follows: righthand end of. transformer secondary 55,wire 1I,

contact point 55, contact Y25, bimetallic element 21,conta-ct 3l,contact point 55, wire 51, wire 55,

to the right, thereby bringing switch arms 55A and 55 into engagementwith contact points 5,5 and 55. Engagement of switch arm 55 with thecon-4 tact point will cause energization of the gas valve 50 throughwire 54, contact 55, switch arm 55, wire 55, valve and wire 5I to theline wire 52. i

Engagement of switch arm 55 with the contact point 55 will complete aholding circuit for relay out the portion of the initial energizingcircuit passing through contact 3l and contact point 35. Upon anincrease in temperature the thermostatic element will swing to the left,first disengaging contacts 3| and 35, and upon a further increase intemperature will disengage contacts 25 and 54. Due to the holdingcircuit previously mentioned, when contact `3| is disengaged from the'contact point 55 the relay coil 52 will continue to be energized andwill remain energized until the temperature surrounding element 21 issufficient to cause contact 25 to be disengaged from contact point 34.Whenrthis occurs the armature 53 and the switch arms 55 and 55 will bemoved to the left, thereby-breaking the valve opening circuit and alsothe holding circuit.

The heating element I5 is preferably'energized by low voltage current.Therefore, one end ofl element I5 is connected by a wire 15 to one endof the secondary 55 of transformer 15. The other end of the heatingelement I5 is connected by a wire 15'to a rheostat 11, this rheostat inturn being connected by a wire 15 to the other end of the transformersecondary 55. By ad- Justingfrheostat 11 the input to the heater I5 maybe varied in order to secure the desired op-` eration from theinstrument.

ment I5 when once adjusted is thus constantly energized to maintain aconstant or unvarying input of heat into the mass element I I.

In operation, the contact points 35 and 55 may be adjusted so as-to openthe gas valve when the temperature of the mass element II is, forlnstance, at body temperature, namely .98 F., and to cause'opening ofthe valve at a slightly lower temperature, .for instance, 96 F. Theenergize- `tion of the heating element will then be ad# justed by therheostat 11 so that under equilibrium. conditions the heat input to themass ele-A ment II will exactly equal the heatv loss from said elementwhen the masstemperature is at comfortable. the room to the sameconditions as surround the occupants andas the temperature of theinstru--v ment is near body temperature, the heat losses from theinstrument as a whole will be substantially proportional to the heatlosses from the human body. Should the temperature in the room decrease,the effect would be to increase the heat loss from the mass I I throughthe water space and the porous jacketv 5. As the .heat input isconstant, sin-increase in heat loss willl cause a reduction intemperature ofthe mass element II and subsequently cause thethermostatic element21 to move contacts 25 and 5I into en- The heatingele-. .K I

gagement with their. respective contact points t 34 and Il, thereby'causingthe gas valve to open vthermostatic element 2l to eii'ect closingof the4 gas valve, thereby shutting olf the flow of heat s to the spacein which the instrument is located.

thus tend` to maintain the same heat loss from Changes of humidity willalso affect the heat u loss from the instrument similarly as they affect.the heat loss from s. human body. For instance,

should the humidity decrease,` the resulting increase in evaporation ofmoisture from the surface of the instrument will cause a reduction intemperature thereof. This reduction in temperature occurring at thesurface of the instrument wiilcause the temperature difference betweenthe mass element Il and'the exterior of the instrument to increase,thereby increasing the new of heat from the mass element II. As the heatinput thereto is constant, this increase in heat loss will result inreduction in temperature of the mass element Il to a point at' which thereduced heat loss, due to the reduced temperature, just balances theheat input. If the reduction in humidity is sufficient the increasedheat loss from the instrument will cause a sumcient lowering intemperature of the mass element Il to eect operation of the thermostaticelement 21 for opening the gas valve. This will cause the ,temperatureof the room to be increased. As noted hereinbefore, the eiIect oftemperature increase in the air surrounding the instrument is to cause areduction in the heat loss therefrom. When the increase in temperaturedue to the operation of the gas burner or other heating means issumcient to decrease the heat loss from the instrument the same amountas the decrease in humidity increased such heat loss, thev heat losswill be the same as occurred before the reduction inv humidity. Thisreduction in heat loss'will cause the tem perature within the masselement il to rise to its original value, thereby placing the heatingmeans out of operation.

In a similar manner, an increase in humidity will cause a decrease inheat loss from the instrument due to the reduction in evaporation ofmoisture from the surface of the instrument caused by such increase inhumidity. This decrease in heat loss will result in the temperature ofthe mass element Il increasing, thereby causing the thermostatic element21 .to place the heating means out of operation. The resulting reductionin temperature within the space due to heat loss through the walls ofthe building, eventually will cause an increase in heat loss from theinstrument to compensate for the decrease in heat loss caused by thereduction in humidity. v

It is apparent, therefore, that the instrument will act to maintain ahigher temperature withstrument due to a reduction in humidity would thehuman body as occurred before the reduction in humidity. The instrument.therefore, acts to adjust the temperature in the room in accordf ancewith the humidity. in order to maintain the proper heat loss from ahuman body to maintain the space in a comfortable condition.

It is to be observed that the instrument is vaffected by air currentswithin the room in theV same manner as the human body would be ai'-fected by such currents. If the space in which the instrument is locatedis drafty, this flow of air will cause an increase in heat loss due tothe increased evaporation of moisture from the surface of the instrumentand also due to conduction or convection of heat from the surface, bythe moving air. The human body is of course similarly affected. Thus, indrafty conditions the 'increase in heat loss from the instrument willcause it to maintain a temperature within the room which is sumcient tocompensate for such drafty conditions, thereby maintaining theproperheat loss from the instrument and also from the human body.Similarly, if the air in the room is'extremely still, the heat loss fromthe instrumentwill be decreased, thereby causing it to maintain a lowertemperature within the en'-l closure in order to compensate for thisstill air condition, thereby maintaining the proper heat loss from thehuman body in order to maintain the occupants comfortable.

The heat loss from the instrument is also affected by the temperature ofthe walls or objects within the room. For instance, should the walls ofthe room be colder than the exterior of the instrument, radiation ofheat from.the surface of the instrument to the walls will take place.This of course will increase the heat loss from the instrument, therebydecreasing the temperature of the mass element -I I. Similarly, shouldthe walls be warmer, a decrease in radiation from the surface of theinstrument to the walls will take place, thereby causing a decrease inheat loss from the instrument. If objects within the room are of highertemperature than the instrument, a radiation of heat from such objectsfrom the instrument will take place,

tionate to the effect on the human body caused by the same conditions.Therefore, if the radiation effects within the enclosure are such aswould l.cause the occupants to feel warm, their effect upon theinstrument will be to decrease the heat loss therefrom sufllciently tocause it to eifect a decrease in room temperature suflicient tocompensate for the effect of the radiation. Similarly, if' the radiationof objects within the room would Acause theoccupants to feel cold, theeffect upon the instrument will be identical. thus causing it toincrease the room temperature suiliciently to compensate for suchradiation conditions.

From the foregoing'it should be apparent that the instrument imitatesthe heat loss from the human body and will act to maintain conditionswithin the room or enclosure such that the resulting heat loss from thehuman body is sumagentscl 5- cent to cause the occupants to feelcomfortable.

In other words, the device is responsive to room of the modulating typewhich is well known in the art. Further, while I have illustrated theheating element as being constantlyenergized to maintain a constantinput of heat, it will be apparent that it may be energizedintermittently or that the input may be varied in accordance with somegiven program.

In Figure 3 I have illustrated a different form of thermostat havingapplied thereto the radiation responsive feature appearing in Figure l.-The thermostat illustrated in this gure is intended for mounting uponthe wall of a room instead of being hung from the ceiling as in the caseof that of Figure l. The thermostatcomprises al base plate 80 adapted tobe secured to the wall of a room or enclosure. A U-shaped thermostaticelement 8| is pivotally secured -to the base plate by means of an ear 03secured to said element, and by a second ear 0I which is secured insuitable manner to the base platel.

.Ears 03 and 80 are pivotal] secured together by means of a pin 80. At te upper end of the base plate v80 is mounted an adjusting device 08,

this device comprising an adjusting wheelll.

mounted upon a stud shaft 00 which is rotatably secured to the baseplate 80. On the side of the adjusting wheel 01 opposite from the studshaft 80 is an adjusting cam 80 which cooperates with the upper end ofthe leg 90 of the U-shaped thermostatic element 8|. A springi is mountedbetween the base plate 80 and the lower end o f the leg 90 of thethermostatic element. Ihis spring urges the upper end of the leg 00against the cam 09. By rotation of the adjusting wheel 81 thethermostatic element is thus tilted one way or the other. The shorterleg 92 of the thermostatic element 0l carries a exible contact blade 03having secured thereto a contact 00. The leg 92 also carries arelatively stil! contact blade 00 which carries a contact 08. Mountedvopposite to the contacts 0l and 00 is a contact point carrying member 01formed of insulating material, this member carrying an adjustablecontact point 00 which cooperates with the contact 94 and also carryingan adjustable contact 90 which cooperates with the contact 90. Forfurther details of this form of thermostat reference is made to thevapplication of Carl G. Kronmiller et al. Serial No'. 55,603 filedDecember 21,- 1935.

A cover |00 is mounted upon the base plate 00 in any suitable manner.This cover has a front face of relatively thick heat conducting ma'-terial, and at its upper and lower ends is provided with slots such' as|0| for permitting the passage of air across the thermostatic element0|. At its upper end, cover |00 is recessed 'at |02 to receive a heatingelement |03. A similar recess |00 is provided in the lower .portion oi.'

.the cover. this recess accommodating a heating element |00. Heatingelements |08 and |00 may 75 heat to the surrounding objects.

be connected together by the leads |08. Leads |'01 and |00 are connectedto the other ends ,of each Aheating element and lead to suitablebindingposts |00.

This thermostat may be wired aI manner illustrated in Figure 2L that is,the heating elements |03 and |00 may be constantly energized to maintaina constant input of heat 'to the cover |00. As the heating elements |00and |00 are in good heat conductive relationship with the cover or masselement |00, thetemperature of the mass |00 will besubstantially equalto the temperature of the heating element. By this' arrangement thetemperature of the cover or mass 'element |00 may be maintained aboveroom temperature, thereby causing this cover to radiate The cover |00 ispreferably given a black surface in order that it may readily radiateheat to the objects within the room, or absorb heat from objects ofhigher temperature.

In operation 4the energization of heating elements |00 and |05 may becontrolled to give the desired amount of heat input to the cover orlmass element |00. The position of the adjusting wheel 01 will then beadjusted so' that the thermostatic element caus engagement with orseparation of the cooperating contacts at a temperature suilicientlyabove room temperature as to compensate for the effect ofv the' heatingof the cover4 or masseiement |00. In other words.

due to thefact that the cover causes a higher temperature to existadjacent thermostatic element 01 than exists in thegroom itself, thethermostatic element must be adjusted to operate at a higher temperaturethan room temperature,

- By properly adjusting the thermostatic element it can be made to openand closethe contacts when the room temperature is that desired, and inthis manner maintain the desired temperature. Should the wallstorobjects within the room be at s low temperature, radiation of heat fromthe cover or mass element |00 to the walls or objects will take piace.As the heat input vis constant the temperature of the mass element |00will decrease. This reduction in temperatin-e will effect thethermostatic element, thereby causing it to close the contacts and placethe heating system into operation. This will result in the roomtemperature increasing and when the room temperature has increased to apoint wherein the increased air temperature compensates for the decreasein temperature caused by increase in radiation from the mass element|00, the thermostatic element will act to place the heating systemout ofoperation. Conversely, should the temperature of the walls orobjects inthe Iroom increase, the Adecrease in radiation from the cover or masselement |00. will causethe temperature -of said element to increase.This will act to cause the thermostatic element to swing its contactstowards the left and sway from the contacts 00 and 00' even though theroom temperature remains the same. Thus. be-

fore the thermostatic 'element 01 will cause operation of the burner theroom ture the' heated radiating cover plate |00 will cause the controlVpoint ofthe thermostat to be variedl in accordance with the temperatureof the walls or other objects in the room or enciosure'and but for thedecrease in radiation from the temperature which will be 6 emessamaintainedin theroom when the wallsor other 'control of panel typeheating systems wherein the heating is ei'lected by heating the wallsand ceiling of the enclosure. With such heating arrangements it isapparent that the ellect of the wall temperature upon human comfort isappreciable and for proper control requires a thermostat which isresponsive to radiation as well as to air temperature.

while in the embodiments of my invention u! lustrated in Figure 1 and inFigure 3. I havel shown the mass elements as being heated by separateheating elements,- it is to be understood that I do not limit myself tothis. `Ii'or instance, if desired the mass element may be formed of -amaterial having good heat conducting characteristics but which o'ersappreciable resisting a low voltage current through the entire mass`element formed of such material, the mass element itself may act as aheater.A Also, while I have shown the maas elements as being relativelythick, it is to be understood that I do not limit myself to this, andthat this term mass as appears in the following claims is not to beconstrued as requiring a thick or massive element. It should be furtherapparent that many other modifications of my inventionwill be apparentto those skilled in the art. For instance, difierent forms of moisturediffusing surfaces may be employed than that shown in Figure 1. Also itis apparent that if desired the thermostat of Figure 3 could be providedwithna moisture diffusingsiu'faoe. It should be further apparent that ifdesired the embodiment of the invention illustrated in Figure 3 couldbemodiiied so that the thermostatic element is responsive solely to themass temperature instead of the combined action of the mass temperatureand air temperature. It will be further apparent that the embodiment ofthe invention illustrated in Figure l could be modiiied so as toallowthe room air to contact the thermostaticA element as in the case ofFigure 3 or the moisture diifusing cover heat conducting materiallocated in said 'en-v v closure and having a centrally locateddepression in the inner surface thereof, heating means lo-1 cated insaid depression in intimate heat conductive relationship with saldi masselement for heating it substantially uniformly throughout, means foroperating said heating means to supply continuously a xed amount of heat-to said mass element in sufllcient quantity to maintain the temperatureof the mass element above the temperature of the air'in the enclosurewhereby the temperature of the mass element is determined by thetemperature of the air in the enclosure, by the amount of air motion inthe enclosure and by the temperature of the walls of the enclosure andoi objects therein, a porous enclosure for said hollow mass element andspaced therefrom, means for supplying water to the space between theporous'enclosure and the hollow mass element to cause moisture to seepthrough the porous enclosure and evaporate on the exterior surfacethereof whereby the temperature of the hollow mass' element is alsoaffected by the relative humidity in the enclosure, thermostatic meanslocated inside of the hollow mass element and influenced substantiallysolely by the temperature of the mass.

2. In apparatus of the character described, a control mechanism forcontrolling a temperature changing means for an enclosure comprising inzo combination, a hollow mass element of heat conducting materiallocated in said enclosure, heating meansl located within said hollowmass in intimate heat conductive relationship with said mass element forheating it substantially unig5 formly throughout, means for operating'said ance to the passage of electricity. Thus, by passheating means tosupply continuously a fixed amount of heat to said mass element insufficient quantity to maintain the temperature of the mass elementabove the temperature of the air in the enclosure whereby thetemperature of the mass element is determined by the temperature of theair in the enclosure, bythe amount of air motion in the enclosure and bythe temperature of the walls of the enclosure and of objects there- 85in, means for supplying moisture to the outside y of the hollow masselement whereby said moisture evaporates on the exterior surface of themass element so as to cause the temperature of the hollow mass elementto be ailected by the 0 relative humidity in the enclosure, andthermostatic Ieans located inside of the hollow mass element andiniluenced substantially solely by the temperature of the said masselement.

3. In `apparatus oi the character described,

control mechanism for controlling a temperature changing means for anenclosure comprising in combination, a hollow mass element of heatconducting material located in said enclosure, heating means located insaid hollow mass element in intimate heat conductive relationship 'withthe element for heating it substantially uniformly throughout, means foroperating said heating Y means tosupply continuously a nxed amount ofheat to said mass element in sumcient quantity to maintain thetemperature of the mass element above the temperature of the air in theenclosure whereby temperature of the mass` element is determined by thetemperature of the air in the enclosure, by the amolmt of air motion inthe enclosure and by the temperature of the walls of the enclosure andof objects therein, a porous enclosure for said hollow mass element andspaced therefrom, means for supplying water to the space between theporous enclosure and the hollow mass element to cause moisture to seepthrough the porous enclosure and evaporate on the exterior surfacethereof whereby the temperature of the hollow mass element is alsoaffected by the relative humidity in the enclosure, and thermostaticmeans located inside of the hollow mass element and iniiuencedsubstantially solely by the temperature of the mass element.

JOHN E. HAlNES.

